We propose to apply physical methods, especially NMR spectroscopy to endocrinology and pharmacology, with special reference to brain peptides involved in physiology, learning and behavior. The primary events viz extracellular binding of the secreted peptide to the membrane-receptor complex in the target tissue and the consequent triggering of intracellular events depends upon recognition by the receptor of the peptide. We will elucidate the conformation and conformational mobility of neuropeptides and their agonists and antagonists with a view to understanding the underlying physico-chemical mechanisms of the recognition/triggering process. IH magnetic resonance spectroscopy will be the principal method used, especially difference spectroscopy, double and triple resonance, the NOE, selective and nonselective relaxation rates. Intracellular secondary events resulting from extracellular binding of hormones have not been studied in intact cells by the non-destructive technique of NMR spectroscopy. Metabolite levels and their peptide-induced changes will be followed by 1H, 31P and 13C. Where necessary isotopically labelled molecules will be used to follow specific metabolic pathways.